1. Field of the Invention
The invention relates to a circuit for horizontal deflection in television picture display devices, including a capacitor arranged in series with the horizontal deflection coil for correcting the tangential error by means of an S-shaped distortion of the deflection current, and to a picture display device including such a circuit.
2. Description of the Related Art
It is known that the geometry of display tubes gives rise to a non-linear distortion of the scanning raster proximate to the beginning and the end of the horizontal scanning line. To correct this non-linearity, a capacitor is normally arranged in series with the horizontal deflection coils. This S correction capacitor used for correcting the tangential error is charged during a part of the horizontal deflection interval and is discharged during another part so that the horizontal deflection current is S-shape modified and the deflection is performed linearly.
In order to achieve a desired extent of S formation at different values, i.e. deflection frequencies, it is known (for example, from DE 34 19 930, corresponding to U.S. Pat. No. 4,516,169) to connect a further capacitor optionally in series or in parallel with this S correction capacitor. Moreover, it is known from EP 0 146 345, corresponding to U.S. Pat. No. 4,533,855, that an improvement of the S correction in display tubes having very large deflection angles or complex display screen shapes can be achieved by temporarily adding a further capacitor during the horizontal or vertical deflection. A drawback thereof is that a circuit should be additionally provided for connecting and disconnecting the further capacitor.